The disclosed embodiments relate to highly integrated and/or modular high-speed aircraft configurations and methods for designing and manufacturing such configurations.
One goal of the commercial air transport industry is to convey passengers and cargo as quickly as possible from one point to another. Accordingly, many commercial transport aircraft operate at cruise Mach numbers of approximately 0.8-0.85. As the time constraints placed on air carriers and their customers increase, it would be advantageous to economically transport passengers and cargo at higher speeds. However, aircraft flying at transonic or supersonic speeds (greater than about Mach 0.85) have greater relative thrust requirements than comparably sized subsonic aircraft. To generate sufficient thrust at high altitudes and Mach numbers, while reducing the corresponding increase in drag, conventional transonic and supersonic aircraft include low bypass ratio turbofan engines or straight turbojet engines. Such configurations generally have a high specific fuel consumption at cruise conditions that generally outweighs any inherent advantage in aerodynamic efficiency, resulting in a net fuel efficiency significantly lower than that of lower speed aircraft. The low fuel efficiency can also result in increased atmospheric emissions.
Conventional transonic and supersonic aircraft generally operate at very high jet velocities to generate sufficient thrust for take-off, which can result in significant airport and community noise problems. One approach to reducing the noise is to lengthen the engine inlet and nozzle ducts, and to also integrate noise abatement treatments with the ducts. One drawback with this approach is that such treatments generally increase the weight of the propulsion system, which can increase the wing structural loads and the susceptibility of the aircraft to wing flutter. If the wings are thickened to increase their weight capacity, the wave drag of the aircraft will also tend to increase. The increased weight of the wings also increases the amount of fuel that must be carried by the aircraft, which in turn increases the weight of the structure to support the fuel, which in turn requires still more fuel. Accordingly, it can be difficult to develop an effective, efficient, environmentally acceptable aircraft that operates at transonic and/or supersonic Mach numbers.
FIGS. 1A and 1B illustrate top isometric and bottom isometric views, respectively, of a supersonic cruise aircraft 100a in accordance with the prior art. The aircraft 100a can include a fuselage 102a, delta wings 104a, a propulsion system 106a suspended from the wings 104a, and an aft-tailed pitch control arrangement 107. Alternatively, the aircraft 100a can include a tail-less or canard pitch arrangement. In either configuration, the longitudinal distribution of the exposed cross-sectional area of the aircraft, and the longitudinal distribution of the planform area tend to dominate the transonic and supersonic wave drag (i.e., the increase in drag experienced beyond about Mach 0.85 due to air compressibility effects). Accordingly, the fuselage 102a can be long, thin, and xe2x80x9carea-ruledxe2x80x9d to reduce the effects of wave drag at supersonic speeds.
Area-ruling the fuselage 102a can result in a fuselage mid-region that is narrower than the forward and aft portions of the fuselage (i.e., a xe2x80x9cwaistedxe2x80x9d configuration). Waisting the fuselage can compensate for the increased cross-sectional area resulting from the presence of the wings 104a and the propulsion system 106a. The propulsion system 106a can include four engine nacelle pods 108a mounted beneath the wing 104a to minimize adverse aerodynamic interference drag and to separate the rotating machinery of the engines from the main wing spar and the fuel tanks located in the wing. Noise suppressor nozzles 110a are typically cantilevered well beyond a trailing edge 112a of the wing 104a, and can accordingly result in large cantilever loads on the wing 104a. 
FIGS. 1C-E illustrate a side view, plan view and fuselage cross-sectional view, respectively, of a configuration for a high-speed transonic cruise transport aircraft 100b having a fuselage 102b, swept wings 104b, and engine nacelles 106b suspended from the wings 104b in accordance with prior art. The fuselage 102b has a significantly narrowed or waisted portion proximate to a wing/body junction 105. Accordingly, the fuselage 102b is configured to avoid or at least reduce increased drag in a manner generally similar to that described above with reference to FIGS. 1A and 1B. This configuration may suffer from several drawbacks, including increased structural weight, increased risk of flutter loads, and a reduced payload capacity. The configurations shown in FIGS. 1A-1E can be structurally inefficient and can have reduced payload capacities as a result of the fuselage waisting required to reduce transonic and supersonic drag.
The present invention is directed toward high-speed aircraft and methods for aircraft manufacture. In one aspect of the invention, the aircraft can include a fuselage portion configured to carry a payload, and a wing portion depending from the fuselage portion. The wing portion can have a forward region with a leading edge, an aft region with a trailing edge, an upper surface, and a lower surface. The aircraft can further include a propulsion system at least proximate to the aft region of the wing portion, with at least part of the propulsion system positioned between the upper and lower surfaces of the wing portion. The propulsion system can include at least one inlet aperture positioned beneath the wing portion lower surface or above the wing portion upper surface, and at least one engine positioned aft of and vertically offset from, the at least one inlet aperture. The propulsion can further include at least one exhaust nozzle aft of the at least one engine. In a further aspect of the invention, the aircraft can further include at least one canard depending from the fuselage portion forward of the propulsion system. In another aspect of the invention, the fuselage portion can be elongated along a fuselage axis and the aircraft can include a pitch control surface having an aft trailing edge positioned inboard of the exhaust nozzle between the exhaust nozzle and the fuselage axis.
In still a further aspect of the invention, the propulsion system can include a rearwardly curving S-shaped duct between the inlet aperture and the engine. The aircraft can be configured to operate at a sustained cruise Mach number of from about 0.95 to about 0.99, or, alternatively, the aircraft can be configured to operate at a sustained cruise Mach number of from about 1.5 to about 3.0. The fuselage portion can include a forward region, an aft region adjacent to the propulsion system, and an intermediate region forward of the propulsion system between the forward and aft regions. The fuselage portion can taper continuously from the intermediate region to the aft region.
The invention is also directed to a modular aircraft system that can include a fuselage portion having a payload section, and a swept-wing portion depending from the fuselage portion and having an upper surface and a lower surface. The aircraft system can further include first and second nose portions interchangeably positionable on the fuselage portion, with the first nose portion being configured for subsonic flight up to about Mach 0.99 and the second nose portion being configured for supersonic flight. The system can further include first and second nacelles interchangeably coupleable to an aft part of the wing portion, with the first nacelle being configured for subsonic flight up to about Mach 0.99 and the second nacelle being configured for supersonic flight.
The invention is still further directed to a method for manufacturing an aircraft. In one aspect of the invention, the method can include attaching a wing portion to a fuselage portion with the wing portion having a forward region with a leading edge, an aft region with a trailing edge, an upper surface and a lower surface. The fuselage portion can be configured to carry a payload and can be elongated along a fuselage axis. The method can further include coupling a propulsion system to the wing portion by mounting the propulsion system to the aft region of the wing portion and positioning at least part of the propulsion system between the upper and lower surfaces of the wing portion. The propulsion system can include at least one inlet aperture positioned beneath the lower surface of the wing portion or above the upper surface of the wing portion, with the propulsion system further including at least one turbofan engine positioned aft and vertically offset from the at least one inlet aperture. The propulsion system can further include at least one exhaust nozzle aft of the at least one engine, and a generally S-shaped duct between the at least one engine and the at least one inlet aperture. The method can still further include positioning a pitch control surface between the propulsion system and the fuselage axis, or attaching a canard to the fuselage portion.